**What is an Electronic Scale?**
An electronic scale, also known as an electronic balance, is a precision measuring device that calculates the weight of objects using principles based on Hooke’s Law or force measurement. These scales are categorized into three main types: mechanical scales, electronic scales, and electromechanical combined scales. An electronic scale typically consists of three key components: a load-bearing system (such as a weighing pan or scale body), a force transmission and conversion system (like a lever mechanism or sensor), and an indication system (such as a digital display or analog dial).
The use of electronic scales has become widespread in both commercial and industrial settings due to their accuracy, ease of use, and ability to provide instant results. Whether for retail, scientific research, or manufacturing, these devices play a crucial role in ensuring precise measurements.
**Design of a Multifunctional Electronic Scale Based on STM32**
This project aims to develop a multifunctional electronic scale that integrates various features such as real-time weight calculation, price display, temperature monitoring, voice feedback, and more. The system is built around the STM32 microcontroller, which provides sufficient processing power and peripheral support for advanced functionality.
**Subject Requirements:**
1. **Basic Part:**
- Set unit price via keyboard, displaying weight, unit price, and total amount simultaneously.
- Use a TFT LCD to show weight (up to 99.999 kg), unit price (up to 999.99 yuan), and total amount (up to 9999.99 yuan) with high accuracy.
- Include a tare function and total accumulation calculation.
- Store prices for up to 10 different items.
- Measure ambient temperature with an error margin of less than 1°C.
- Weigh objects between 0-10 kg.
- Provide voice output for measurement results.
2. **Advanced Features:**
- Display real-time clock (year, month, day, hour, minute, second) with power-down protection.
- Enhance measurement accuracy using a high-precision 24-bit ADC (HX711).
- Store item names and pre-set prices for 10 products.
**Module Design:**
1. Main control chip module (STM32)
2. TFT color LCD module
3. Weighing module (HX711 + load cell)
4. Voice broadcast module (WT588D)
5. 24-bit ADC HX711 conversion module
6. Software implementation
**Module Introduction:**
**1. Main Control Chip Module – STM32**
The STM32 series microcontroller is chosen for its high performance, low power consumption, and rich set of peripherals. It supports multiple communication interfaces, including SPI, I2C, UART, and USB, making it ideal for complex systems like this electronic scale. Its 32-bit ARM Cortex-M3 core ensures fast processing and efficient handling of data from sensors and other modules.
**2. TFT Color LCD Module**
This module offers a resolution of 320x240 pixels with 16-bit true color display. It includes a resistive touch screen for user interaction. The interface is compatible with various development boards, allowing flexibility in hardware design.
**3. Weighing Module**
The weighing system uses a load cell connected to the HX711 24-bit ADC. This setup ensures high precision in weight measurement. The load cell is installed using a cantilever beam method, and the signal is transmitted through a four-wire configuration.
**4. Voice Broadcast Module – WT588D**
The WT588D is a versatile voice chip that allows for easy programming and playback of audio messages. It supports PWM and DAC output modes, with PWM being used here for cost-effective speaker driving. The module can be controlled via a serial interface and is ideal for providing audible feedback during weighing.
**5. 24-bit ADC HX711 Module**
The HX711 is a highly integrated A/D converter designed specifically for weight sensing applications. It features built-in amplifiers, a voltage regulator, and a clock oscillator, reducing the need for external components. It supports two differential input channels, making it suitable for multi-channel weighing systems.
**6. Software Implementation**
The software includes functions for initializing the TFT display, reading values from the HX711, controlling the voice module, and managing user input. Key functions include:
- `LCD_Init()` – Initialize the display
- `Read_HX711()` – Read weight data
- `pronounce_num()` – Convert numbers to speech
- `UI()` – Manage the user interface
By combining these components, the system achieves accurate and user-friendly weight measurement with enhanced functionality, making it suitable for a wide range of applications.
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